1. Field of the Invention
The present invention relates to a multifunctional optical sheet having a light shielding property. More particularly, the present invention relates to a multifunctional optical sheet having a light shielding property, which includes polycarbonate, a metal mixture, that is composed of chrome, iron, and nickel, and a pigment, and which can improve visible light transmittance while intercepting infrared rays.
2. Description of the Prior Art
In general, polycarbonate (PC) sheets have been widely used in place of glass as construction materials for skylights, lighting panels for buildings, roofing materials, canopy, windows and doors or safety glass, swimming pools, roofs of gymnasiums, greenhouses, or soundproofing walls.
Since such a polycarbonate sheet has superior transparency, strength, and scratchproof, it is formed on an upper surface and a lower surface of a glass fiber layer and serves to supplement the mechanical strength of the glass fiber layer.
Sunlight is briefly divided into ultraviolet rays (UV), visible light rays (VIS), and infrared rays (IR). Specifically, the sunlight includes about 6% of ultraviolet rays, about 46% of visible light rays, and about 48% of infrared rays, and thus almost a half of the sunlight is occupied by the infrared rays which do not contribute to the lighting, but have a thermal effect. The infrared rays are classified into near infrared rays (0.75 to 3 μm), infrared rays (3 to 25 μm), and far infrared rays (exceeding 25 μm) in accordance with their wavelengths. The infrared rays have the feature in that they have a strong thermal effect in comparison to the visible light rays or ultraviolet rays, and thus are also called heat rays. The radiant heat that is delivered from the sun or a heating element to an indoor space is caused by the infrared rays.
However, a polycarbonate sheet in the related art that has been used for an outdoor structure has problems in that since it has a low infrared shielding effect, the internal temperature of the structure is increased especially on summer time, and sheet bending occurs due to thermal expansion and shrinkage.
In order to solve the problems, various methods for obtaining thermal insulation effects, such as using a milky white polycarbonate sheet, laminating an infrared reflection film on one surface of a polycarbonate sheet, and coating an infrared reflection layer on one surface of a polycarbonate sheet, have been used.
However, in the case of using the milky white polycarbonate sheet, it easily gets dirty, and its external appearance becomes unclean. In the case of forming an infrared reflection film or an infrared reflection layer, a separate lamination process or deposition process for forming the infrared reflection film or infrared reflection layer is required to deteriorate the productivity. Further, the infrared reflection layer easily peels off and is easily worn away to shorten the period of use.